Xerophthalmia is a leading cause of world blindness. Clinical and experimental observations have led to the central hypothesis that he vitamin A-deficient (A-) cornea is abnormally susceptible to trauma and infection, leading to an abnormally accelerated inflammatory response, increased collagenolytic activity, and resultant stromal ulceration (keratomalacia). The long-term objective is to establish to interrelationship between vitamin A status and the abnormal corneal response to injury and infection. This will improve understanding of the pathogenesis of xerophthalmia and the treatment of keratomalacia. A well-characterized nutritional model, the A- rat, will be utilized in clinical, biochemical, immunologic, and morphologic studies. The proposed Specific Aims are as follows: 1. Wound healing: to determine why A- corneal epithelium is wounded easily and heals slowly. (Ultrastructural morphometric analysis will quantitate abnormality of the corneal epithelia adhesion complexes, and in vivo and organ culture studies will further characterize the known deficiencies of fibronectin and plasminogen activator in the healing A- cornea.) 2. Infection: to examine the mechanism of increased bacterial adhesion to the A- ocular surface. (Concanavalin A binding to the surface glycoproteins of unwounded A- corneal epithelium will be ultrastructurally quantitated. Bacterial adhesion to corneal epithelium through mannose residues will be determined by SEM.) 3. Inflammation: to detect chemotactic factors (CF) for polymorphonuclear neutrophils in A- corneas that could account for the abnormal inflammatory response after minor wounding. (Boyden chamber methodology will assess CFs from wounded A- corneas, and specific assays will quantitate C5a, IL-1, and possibly unique CFs in A- corneas.) 4. Ulceration: to characterize the source of collagenase in injured A- corneas and to examine protease gene expression and activity in A- keratocytes. (Enzymatic and immunoassays will complement studies using a cDNA probe for protease mRNA to characterize the interactions of A- corneal epithelium, keratocytes, and polymorphonuclear neutorphils in vitro.)